Near-white-light emissive upconversion NaYF4:50%Yb,2%Er@NaYbF4:1%Tm@NaYF4 nanoparticles for the ratiometric fluorescence detection of sulfite

Abstract

White light plays an important role in the field of sensing because of its sensitive color responses to targets. In this study, core–shell–shell structural NaYF₄:50%Yb,2%Er@NaYbF₄:1%Tm@NaYF₄ nanoparticles (NWL-UCNPs) with multiple narrow emissions were designed to emit near-white light by tuning their emission intensity in the violet, blue and green (VBG) ranges. The main mechanisms involved the spatial separation of Tm³⁺ and Er³⁺ and their optimized concentration proportion of 1% to 2%. By taking advantage of the inner filter effect (IFE) between the NWL-UCNPs and pararosaniline (PAR), a ratiometric fluorescence strategy was developed to detect sulfite, which exhibited the advantages of easy visualization, rapid response, high sensitivity and selectivity. The detection limit was 112 nM, and the linear range was 1–150 μM. It also exhibited good recovery rates ranging from 91.36% to 105.09%, with relative standard deviations of 0.13–3.39%. Thus, our work proposed a feasible strategy to fabricate NWL-UCNPs, which emit near-white light under 980 nm excitation and developed a ratiometric fluorescence strategy for rapid and visual detection of sulfite.